/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package cn.ieclipse.af.adapter;

import android.annotation.TargetApi;
import android.app.Fragment;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.os.Build;
import android.os.Parcelable;
import android.support.v4.view.PagerAdapter;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;

/**
 * Modify from android.support.v13.FragmentPagerAdapter.
 * 
 * 
 * Implementation of {@link android.support.v4.view.PagerAdapter} that
 * represents each page as a {@link android.app.Fragment} that is persistently
 * kept in the fragment manager as long as the user can return to the page.
 *
 * <p>
 * This version of the pager is best for use when there are a handful of
 * typically more static fragments to be paged through, such as a set of tabs.
 * The fragment of each page the user visits will be kept in memory, though its
 * view hierarchy may be destroyed when not visible. This can result in using a
 * significant amount of memory since fragment instances can hold on to an
 * arbitrary amount of state. For larger sets of pages, consider
 * {@link FragmentStatePagerAdapter}.
 *
 * <p>
 * When using FragmentPagerAdapter the host ViewPager must have a valid ID set.
 * </p>
 *
 * <p>
 * Subclasses only need to implement {@link #getItem(int)} and
 * {@link #getCount()} to have a working adapter.
 *
 * <p>
 * Here is an example implementation of a pager containing fragments of lists:
 *
 * {@sample development/samples/Support13Demos/src/com/example/android/supportv13/app/FragmentPagerSupport.java
 * complete}
 *
 * <p>
 * The <code>R.layout.fragment_pager</code> resource of the top-level fragment
 * is:
 *
 * {@sample development/samples/Support13Demos/res/layout/fragment_pager.xml
 * complete}
 *
 * <p>
 * The <code>R.layout.fragment_pager_list</code> resource containing each
 * individual fragment's layout is:
 *
 * {@sample development/samples/Support13Demos/res/layout/fragment_pager_list.xml
 * complete}
 */
public abstract class AfFragmentPagerAdapter extends PagerAdapter {
    private static final String TAG = "FragmentPagerAdapter";
    private static final boolean DEBUG = false;
    
    private final FragmentManager mFragmentManager;
    private FragmentTransaction mCurTransaction = null;
    private Fragment mCurrentPrimaryItem = null;
    
    public AfFragmentPagerAdapter(FragmentManager fm) {
        mFragmentManager = fm;
    }
    
    /**
     * Return the Fragment associated with a specified position.
     */
    public abstract Fragment getItem(int position);
    
    @Override
    public void startUpdate(ViewGroup container) {
    }
    
    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        if (mCurTransaction == null) {
            mCurTransaction = mFragmentManager.beginTransaction();
        }
        
        final long itemId = getItemId(position);
        
        // Do we already have this fragment?
        String name = makeFragmentName(container.getId(), itemId);
        Fragment fragment = mFragmentManager.findFragmentByTag(name);
        if (fragment != null) {
            if (DEBUG)
                Log.v(TAG, "Attaching item #" + itemId + ": f=" + fragment);
            mCurTransaction.attach(fragment);
        }
        else {
            fragment = getItem(position);
            if (DEBUG)
                Log.v(TAG, "Adding item #" + itemId + ": f=" + fragment);
            mCurTransaction.add(container.getId(), fragment,
                    makeFragmentName(container.getId(), itemId));
        }
        if (fragment != mCurrentPrimaryItem) {
            // FragmentCompat.setMenuVisibility(fragment, false);
            // FragmentCompat.setUserVisibleHint(fragment, false);
            setMenuVisibility(fragment, false);
            setUserVisibleHint(fragment, false);
        }
        
        return fragment;
    }
    
    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        if (mCurTransaction == null) {
            mCurTransaction = mFragmentManager.beginTransaction();
        }
        if (DEBUG)
            Log.v(TAG, "Detaching item #" + getItemId(position) + ": f="
                    + object + " v=" + ((Fragment) object).getView());
        mCurTransaction.detach((Fragment) object);
    }
    
    @Override
    public void setPrimaryItem(ViewGroup container, int position,
            Object object) {
        Fragment fragment = (Fragment) object;
        if (fragment != mCurrentPrimaryItem) {
            if (mCurrentPrimaryItem != null) {
                // FragmentCompat.setMenuVisibility(mCurrentPrimaryItem, false);
                // FragmentCompat.setUserVisibleHint(mCurrentPrimaryItem, false);
                setMenuVisibility(mCurrentPrimaryItem, false);
                setUserVisibleHint(mCurrentPrimaryItem, false);
            }
            if (fragment != null) {
                // FragmentCompat.setMenuVisibility(fragment, true);
                // FragmentCompat.setUserVisibleHint(fragment, true);
                setMenuVisibility(fragment, true);
                setUserVisibleHint(fragment, true);
            }
            mCurrentPrimaryItem = fragment;
        }
    }
    
    @Override
    public void finishUpdate(ViewGroup container) {
        if (mCurTransaction != null) {
            mCurTransaction.commitAllowingStateLoss();
            mCurTransaction = null;
            mFragmentManager.executePendingTransactions();
        }
    }
    
    @Override
    public boolean isViewFromObject(View view, Object object) {
        return ((Fragment) object).getView() == view;
    }
    
    @Override
    public Parcelable saveState() {
        return null;
    }
    
    @Override
    public void restoreState(Parcelable state, ClassLoader loader) {
    }
    
    /**
     * Return a unique identifier for the item at the given position.
     *
     * <p>
     * The default implementation returns the given position. Subclasses should
     * override this method if the positions of items can change.
     * </p>
     *
     * @param position
     *            Position within this adapter
     * @return Unique identifier for the item at position
     */
    public long getItemId(int position) {
        return position;
    }
    
    private static String makeFragmentName(int viewId, long id) {
        return "android:switcher:" + viewId + ":" + id;
    }
    
    private void setMenuVisibility(Fragment f, boolean isVisible) {
        f.setMenuVisibility(isVisible);
    }
    
    @TargetApi(15)
    private void setUserVisibleHint(Fragment f, boolean isVisible) {
        if (Build.VERSION.SDK_INT >= 15) {
            f.setUserVisibleHint(isVisible);
        }
        
    }
}
